Methods and systems for capacitive motion sensing and position control

ABSTRACT

A system for detecting motion and proximity by determining capacitance between a sensor and an object. The sensor includes sensing surfaces made of a thin film of electrically conductive material mounted on a non-conductive surface. In another embodiment, the sensor is a human body. The sensor senses the capacitance between a sensor&#39;s surface and an object in its vicinity and provides the capacitance to a control system that directs machine movement. Because the sensor does not require direct contact or line-of-sight with the object, a machine can be controlled before harm occurs to the object.

BACKGROUND OF THE INVENTION

[0001] This invention relates generally to devices used to providesafety for humans in proximity with moving equipment, and morespecifically to motion and proximity sensors employed as part of acontrol system to orient equipment based on capacitance.

[0002] Safety is important when people are close to moving machines. Onesuch example is locally controlled machines or robotic equipment wherepeople are in close proximity to moving mechanical components. Anotherexample is in the medical imaging equipment industry.

[0003] In known systems, conventional safety mechanisms such asmechanical switches and fluid-filled bladders connected to pressureswitches are typically mounted directly to the moving mechanicalcomponents, or in proximity of the hazardous area. These conventionalsafety mechanisms require direct contact between the person or inanimateobject and the safety mechanism to operate. For example, thefluid-filled bladder mounted to a moving mechanical component uses apressure sensor or a pressure switch inside the bladder to detectincreased pressure as the bladder makes contact with an object. Thesensed pressure increase typically is an input to a control system whichstops the moving mechanical component.

[0004] In other known systems, plates, levers, cables, and rings areconnected to mechanical switches and mounted on the moving mechanicalcomponent. The switches are activated when the plate, lever, cables, orring contacts the person or object, and the machine is stopped beforeany harm occurs.

[0005] Disadvantages of the above described systems include expense(fluid-filled bladders) and the fact that the sensing area is highlylocalized (mechanical switches). Such devices are typically ON or OFFand therefore provide no information to the control system regardingrelative distance between the subject and the sensor. systems. Thedrawback to those systems is that an unobstructed line-of-sight betweenthe detector and the subject is required. As applied to medical imagingequipment, required sterile covers and drapes preclude use ofline-of-sight proximity detector systems. Depending on theimplementation specifics, these sensors are also highly directional andimpacted by object properties such as reflectivity and specularity,which further limits their applicability.

[0006] In the listed examples, safety cannot be enhanced, nor injuryprevented simply by increasing the distances between man and machinebecause each example requires close proximity between man and machine.It would therefore be desirable to provide a system whereby proximityand relative distance to a person or an object can be sensed and theinformation regarding proximity and distance used to control movementand prevent contact with the person or object and thereby increase thesafety of such a system.

BRIEF SUMMARY OF THE INVENTION

[0007] In one aspect, the present invention relates to a method andsystem for detecting motion using a capacitance between a sensor and anobject. Alternatively, the invention detects proximity of an objectusing the capacitance between a sensor and the object. In an exemplaryembodiment, a capacitance based proximity sensor is used as a detector.The sensor includes sensing surfaces made of a thin film of electricallyconductive material mounted on a non-conductive surface. Thenon-conductive surface can take any shape and form. The sensor sensesthe capacitance between a conductive surface and an object placed in itsvicinity, and the sensor provides a capacitance value to a controlsystem. The control system is programmed to use the capacitance data tocontrol the movement of a machine or piece of equipment. In oneembodiment, the piece of equipment is a medical imaging system.

[0008] In another embodiment, the sensing surface is a human body. Arelative capacitance between the human body and surrounding objects isdetermined. The control system uses the capacitance information todetermine a position of the body and proximity of objects near the bodyto control movement of a machine or piece of equipment.

[0009] Accordingly, because the sensor can take any size and shape, anddoes not require direct contact or line-of-sight with the object todetermine if an object has moved, a machine or piece of equipment can becontrolled before harm occurs to the object.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a diagram showing a system for detecting capacitancechange based upon movement;

[0011]FIG. 2 is a diagram showing an alternative system for detectingcapacitance based upon movement;

[0012]FIG. 3 is a diagram showing one embodiment of a capacitance basedproximity sensor;

[0013]FIG. 4 is a diagram showing an alternative embodiment of acapacitance based proximity sensor;

[0014]FIG. 5 is a diagram of a third embodiment of a capacitance basedproximity sensor;

[0015]FIG. 6 is a diagram of a fourth embodiment of a capacitance basedproximity sensor;

[0016]FIG. 7 is a diagram of a sensing field for a capacitance basedproximity sensor;

[0017]FIG. 8 is a diagram of a sensing field for a capacitance basedproximity sensor shaped by sensor surface geometry;

[0018]FIG. 9 is a diagram of a medical imaging system using capacitivebased proximity sensors; and

[0019]FIG. 10 is an illustration of an irregularly shaped apparatus withan outer surface covered with sensing material.

DETAILED DESCRIPTION OF THE INVENTION

[0020]FIG. 1 is a diagram showing a system 10 for detecting capacitancechange based upon movement of, or proximity to, an object 12. Object 12is connected to a capacitance sensing circuit 14 via a conductive strap16. Sensing circuit 14 senses capacitance and supplies data relating tothe measured capacitance to control system 18. Object 12 is on a surface20 which includes a non-conductive surface 22 such as a film or matplaced upon a conductive surface 24. Control system 18 is programmed touse the measured capacitance data to control movement of component 26 inboth horizontal and vertical axes via a motor 28. Component 26 in oneembodiment is a radiation source. Component 26 in an alternativeembodiment is a detector. Component 26 in a further alternate embodimentis a sensor. Component 26 in a still further embodiment is a nuclearmedicine imaging source. Component 26 in another embodiment is a lasersource. Component 26 in yet another embodiment is a component of amedical system, e.g., computer aided tomography (CAT), magneticresonance imaging (MRI), computed tomography (CT), digital fluoroscopy,positron emission tomography (PET), positron emission transaxialtomography (PETT), and mammography.

[0021] The amount of capacitance sensed by circuit 14 changes as object12 moves. In another embodiment, the capacitance sensed also changes asa proximity of object 12 changes with respect to component 26. Thechange in capacitance is received by control system 18 which in turncauses changes in predetermined movement of component 26 such that thetrajectory of object 26 is optimized for a procedure being performed. Anability to detect unexpected motion of object 12 provides control system18 or an operator of control system 18 with a signal to slow or stopmovement of component 26 to prevent injury to object 12 or damage to theabove described equipment. Capacitance sensing circuit 14 is capable ofmeasuring small changes (15-30 femtoFarads) in capacitance. Since anobject 12 changes capacitance as object 12 moves, raising of arms,crossing of legs, finger wiggling, toe wiggling, and torso motion areall detectable.

[0022] Capacitance sensing circuit 14 uses charge transfer technology tomeasure the capacitance of object 12 connected to circuit 14. Conductivestrap 16 is used, along with circuit 14 to measure an effective nominalcapacitance of object 12. Capacitance sensing circuit 14 is manually orautomatically re-calibrated for new nominal capacitive loads, such as,for example a different object 12. The re-calibration process changesthe nominal capacitance about which small changes, such as the movementof object 12 described above, are detected. Re-calibration allows system10 to accommodate objects 12 of different sizes, shapes, clothing, andbody hair, for example. Re-calibration also can take into account theenvironment object 12 is placed, such as temperature and relativehumidity.

[0023]FIG. 2 shows an alternative embodiment to the system shown in FIG.1 employing an alternative method for the measurement of capacitance.Non-conductive surface 22 and conductive surface 24 are as describedabove, however, a conductive mat 40 is placed on top of non-conductivesurface 22 and is electrically connected to capacitive sensing circuit14. The measured capacitance is based upon an amount of object 12actually touching conductive mat 40, as well as movement of object 12,such as raising of arms, crossing of legs, finger wiggling, toewiggling, and torso motion. For instance, the measured capacitance of ahuman body laying supine on mat 40 will be greater than the measuredcapacitance of a human body laying supine on mat 40 with both legs bentand the soles of the feet resting flat on mat 40. As object 12 moves andless of the body is touching mat 40, the measured capacitance willdecrease. The larger the surface area touching mat 40, the higher thecapacitance.

[0024] The embodiments shown in FIGS. 1 and 2 demonstrate, for example,how a human body, can be used as a detector for a capacitive sensingcircuit. Measured capacitance depends on the location of objectsrelative to the body, and other objects or persons near the subjectbeing used as a detector can be detected. Using a subject as a detectormay be ideal when there is the potential for a number of movingcomponents to make contact with the subject, a sensor being installed onevery moving component being unfeasible.

[0025]FIG. 3 is a diagram showing one embodiment of a capacitance basedproximity sensor 50 used in systems where the subject is not used as thedetector. Sensor 50 includes a sensing surface 52 which is made of athin film of conducting material mounted on a front side 54 ofnon-conductive backing material 56. A backing surface 58 of electricallygrounded thin film conducting material mounted on a back side 60 ofnon-conductive backing material 56 completes the sensor. As statedabove, backing surface 58 is connected to an electrical ground 62.Sensing surface 52 is electrically connected to a capacitive sensingcircuit 64 and as shown in FIG. 3, may be configured to be of a sizesmaller in surface area than that of backing material 56.

[0026]FIG. 4 is a diagram showing an alternative embodiment of acapacitance based proximity sensor 70. Sensor 70 is cylindrically shapedand consists of sensing surfaces 72, 74 and 76 of the thin filmelectrically conductive material. Sensing surface 72 covers an outersurface of sensor 70 and sensing surfaces 74 and 76 cover end surfacesof the cylinder, a top surface and a bottom surface respectively.Non-conductive backing material 78 is the “body” of the cylinder, givingsensor 70 strength and a surface for the mounting of surfaces 72, 74 and76 which are electrically connected to a capacitive sensing circuit. Abacking surface (not shown) is electrically connected to ground. Inanother embodiment, the backing surface is not utilized by sensor 70.

[0027]FIG. 5 is a diagram of one embodiment of a proximity sensor 90configured to shape the sensing field. Sensor 90, in the embodimentshown in FIG. 5 consists of an outer sensing surface 92, a centralsensing surface 94, and an inner sensing surface 96. Outer sensingsurface 92, central sensing surface 94 and inner sensing surface 96 areelectrically connected with conductive strips 98 to form an electricallycontinuous circuit and are mounted on non-conductive backing material100. In one exemplary embodiment, sensor 90 has sensing surfacedimensions where inner sensing surface 96 has a dimension of 3 cm×3 cm,a space of 3 cm separates inner sensing surface 96 from an innercircumference 102 of central sensing surface 94 which is 3 cm wide.Another 3 cm gap in sensing material separates an outer circumference104 of central sensing surface 94 from an inner circumference 106 ofouter sensing surface 92. Outer sensing surface 92 is 3 cm in width. Inthe exemplary embodiment, backing material 100 is fabricated from mylar,which is virtually invisible to x-ray radiation. The thickness of themylar backing depends on mechanical strength requirements of anapplication. The sensing surfaces of sensor 90 are variable in size andin number in order to shape the sensing field of sensor 90 and areconnected to a capacitive sensing circuit 108. In the exemplaryembodiment, sensing surfaces 92, 94 and 96 of sensor 90 are fabricatedfrom 3 um thick aluminum foil and bonded to the mylar. In anotherembodiment, aluminum plates are bonded to the mylar. To be invisible toa vascular spectrum, surfaces 92, 94 and 96 are fabricated from aluminumfoil/plates less than 5 um in thickness. In a further embodiment,sensing surfaces 92, 94 and 96 are fabricated from copper. In a stillfurther embodiment, sensing surfaces 92, 94 and 96 are fabricated fromtin.

[0028]FIG. 6 is a diagram of an alternative circular embodiment of aproximity sensor configured to shape the sensing field. Sensor 110, inthe embodiment shown in FIG. 6 consists of an outer sensing surface 112,a central sensing surface 114, and an inner sensing surface 116. Outersensing surface 112 and central sensing surface 114 are ring shaped.Inner sensing surface 116 is circularly shaped. Outer sensing surface112, central sensing surface 114, and inner sensing surface 116 areelectrically connected with conductive strips 118 to form anelectrically continuous circuit and are mounted on non-conductivebacking material 120. In one exemplary embodiment, sensor 110 hassensing surface dimensions where inner sensing surface 116 has adiameter of 3 cm. A ring shaped space 122 that is 3 cm wide separatesinner circular sensing surface 116 from central sensing surface 114.Central circular sensing surface 114 has a inner ring 124 and an outerring 126. Inner ring 124 has a diameter of 9 cm and outer ring 126 has adiameter of 12 cm, such that central sensing surface 114 has a sensorring area of 3 cm in diameter. Another 3 cm wide ring shaped space 128in sensing material separates central sensing surface 114 from outersensing surface 112. Outer sensing surface 112 has an inner ring 130 andan outer ring 132. Inner ring 130 has a diameter of 21 cm and outer ring132 has a diameter of 27 cm, such that outer sensing surface 112 has asensor ring area of 3 cm in diameter. In the exemplary embodiment,backing material 120 is fabricated from mylar, which is virtuallyinvisible to x-ray radiation. The thickness of the mylar backing dependson mechanical strength requirements of an application. The sensingsurfaces of sensor 110 are variable in size and in number in order toshape the sensing field of sensor 110 and are connected to a capacitivesensing circuit 133. In the exemplary embodiment, sensing surfaces 112,114 and 116 of sensor 110 are fabricated from 3 um thick aluminum foiland bonded to the mylar. In another embodiment, aluminum plates arebonded to the mylar. To be invisible to a vascular spectrum, surfaces112, 114 and 116 are fabricated from aluminum foil/plates less than 5 umin thickness. In a further embodiment, sensing surfaces 112, 114 and 116are fabricated from copper. In a still further embodiment, sensingsurfaces 112, 114 and 116 are fabricated from tin.

[0029]FIG. 7 is a diagram 134 of a sensing field for a capacitance basedproximity sensor where no shaping has been employed, for example, wherethe sensing surface is a solid rectangular or square thin-filmconductor. Such a sensor is able to detect capacitive changesomni-directionally. The sensor which produces the type of field shown inFIG. 7 is more sensitive to objects which approach the sensor along anx=0 axis 136 and less sensitive to objects approaching along a y=0 axis138. Objects moving along axis 136 are detected more quickly and from afarther distance. This non-uniform sensitivity is not particularlydesirable.

[0030]FIG. 8 is a diagram of a sensing field 140 where the sensingsurface has been shaped using sensor 90, as described above and shown inFIG. 5. In one embodiment, annular surfaces 92, 94, and 96 are optimizedto flatten the field at a 5 cm distance. The field shown is more uniformcompared to the field shown in FIG. 8, and is illustrative of an abilityto customize field shaping by using segmented sensing surfaces. Thecircular construction used for field shaping can be extended to circularand cylindrical geometries (shown in FIG. 6).

[0031]FIG. 9 is a diagram of a medical imaging system 160 usingcapacitive based proximity sensors 162 electrically connected tocapacitive sensing circuits 164. Capacitive sensors 162 also provide anon-contact method of measuring the relative capacitance of a human bodycovered in paper, plastic and clothing. Circuits 164 provide data to acontrol system 166 regarding position and orientation of component 168relative to 170. Component 168 in one embodiment is a radiation source.Component 168 in an alternative embodiment is a detector. Component 168in a further alternate embodiment is a sensor. Component 168 in a stillfurther embodiment is a nuclear medicine imaging source. Component 168in another embodiment is a laser source. Component 168 in yet anotherembodiment is a component of a medical system, e.g., computer aidedtomography (CAT), magnetic resonance imaging (MRI), computed tomography(CT), digital fluoroscopy, positron emission tomography (PET), positronemission transaxial tomography (PETT), and mammography. Although notshown in the figure, system 166 controls elevation, longitudinalmovement and horizontal orientation of component 168. By using acapacitive based proximity approach, system 166 is configurable tofollow the contours of an object, such as a body 170. System 166 canthen be programmed to optimize the trajectory of component 168 relativeto the object 170. In an exemplary embodiment, system 166 reducesexposures to radiation to body 170 compared to known systems, whicheither do not change the radiation source, detector elevations, oremploy sensing devices, and which require a touching of body 170 beforea control system adjusts movement of component 168.

[0032]FIG. 10 is an illustration of an irregularly shaped apparatus 180with an outer surface 182 covered with sensing material 184. Sensingmaterial 184 is fabricated from a thin-film conducting material, e.g.,aluminum, copper or tin. In an exemplary embodiment, thin-film sheets ofcopper foil are joined together with conductive epoxy 186. In oneembodiment, the copper foil is 25 um in thickness. In an alternativeembodiment, the thin-film sheets are fabricated by “spray depositing” afilm of conductive material, e.g., tin, to a backing surface. Sensingmaterial 184 is bonded to a backing surface (not shown). In analternative embodiment, apparatus 180 is configured to take any form andshape and is not limited to a certain size range. In addition, sensingmaterial 184 is electrically coupled to a capacitive sensing circuit(not shown). Apparatus 180 has one sensing zone 188. In an alternativeembodiment, sensing material 184 has a plurality of sensing zones 188.Sensing zone 188 is capable of measuring changes in capacitance, e.g.,15-30 femtoFarads. In one embodiment, sensing zone 188 is optimized fordetecting predetermined objects at a specified distance. In analternative embodiment, apparatus 180 includes a plurality of sensingzones, each sensing zone optimized to detect a predetermined object at aspecified distance.

[0033] While the invention has been described in terms of variousspecific embodiments, those skilled in the art will recognize that theinvention can be practiced with modification within the spirit and scopeof the claims.

What is claimed is:
 1. A method for detecting motion of an object usinga capacitance based sensing and control system, said method comprisingthe steps of: sensing a presence of the object based on measuredcapacitance between a sensor and the object; sensing a change incapacitance of the object; and adjusting operation of the control systembased upon said sensed capacitance change.
 2. A method according toclaim 1 wherein said step of sensing a presence of the object furthercomprises the step of measuring charge transfer to determine therelative capacitance of the object.
 3. A method according to claim 1further comprising the step of recalibrating the control system when atleast one of a new, nominal capacitive load is detected and at a user'sdiscretion.
 4. A method according to claim 1 wherein said step ofsensing a change in capacitance further comprises the step of sensingchanges in the geometry of the object.
 5. A method according to claim 1wherein said step of sensing a change in capacitance further comprisesthe step of sensing proximity of the object to other objects.
 6. Amethod in accordance with claim 1 wherein the sensor is a human body. 7.A capacitance based proximity sensor comprising: a sensing surface ofthin film conducting material; and a non-conducting backing materialcomprising a front side and a back side, said sensing surface mounted onsaid front side.
 8. A sensor according to claim 7 wherein said sensorfurther comprises an optional backing surface of conducting materialupon which said back side of said non-conducting backing material ismounted.
 9. A sensor according to claim 7 wherein said sensing surfaceis electrically coupled to a capacitance sensing circuit.
 10. A sensoraccording to claim 8 wherein said optional backing surface iselectrically coupled to a circuit ground.
 11. A sensor according toclaim 7 wherein said sensor is configured to be cylindrically shaped.12. A sensor according to claim 11 wherein said sensing material isconfigured to cover an outer surface and both end surfaces of thecylinder.
 13. A sensor according to claim 7 wherein said sensor isrectangularly shaped.
 14. A sensor according to claim 13 wherein saidsensing surface is configured to be of a smaller surface area than saidbacking material.
 15. A sensor according to claim 13 wherein saidrectangularly shaped sensor is approximately 20 cm both length andwidth.
 16. A sensor according to claim 13 wherein said sensing surfacecomprises a plurality of electrically connected rectangular shapedconductors, said rectangular conductors each having an inner dimensionand an outer dimension.
 17. A sensor according to claim 16 comprisingthree rectangular shaped conductors.
 18. A sensor according to claim 17wherein a first rectangularly shaped conductor comprises an innerdimension of 0 cm and an outer dimension of 1.5 cm, a secondrectangularly shaped conductor comprises an inner dimension of 4.5 cmand an outer dimension of 7.5 cm, and a third rectangularly shapedconductor comprises an inner dimension of 10.5 cm and an outer dimensionof 14.75 cm.
 19. A sensor according to claim 7 wherein said sensor iscircularly shaped.
 20. A sensor according to claim 19 wherein saidsensing surface is configured to be of a smaller surface area than saidbacking material.
 21. A sensor according to claim 19 wherein saidcircularly shaped sensor is approximately 21 cm in diameter.
 22. Asensor according to claim 19 wherein said sensing surface comprises aplurality of electrically connected circularly shaped conductors, saidcircular conductors each having an inner dimension and an outerdimension.
 23. A sensor according to claim 22 comprising three circularshaped conductors.
 24. A sensor according to claim 23 wherein a firstcircularly shaped conductor comprises a diameter of 3 cm, a second ringshaped conductor comprises an inner diameter of 9 cm and an outerdiameter of 15 cm, and a third ring shaped conductor comprises an innerdiameter of 21 cm and an outer diameter of 27 cm.
 25. A sensor accordingto claim 7 wherein said sensor is irregularly shaped.
 26. A sensoraccording to claim 25 wherein said sensing surface is configured to beof a smaller surface area than said backing material.
 27. A sensoraccording to claim 25 wherein said irregularly shaped sensor isapproximately 21 cm in length and width.
 28. A sensor according to claim25 wherein said sensing surface comprises a plurality of electricallyconnected irregularly shaped conductors, said irregularly shapedconductors each having an inner dimension and an outer dimension.
 29. Asensor according to claim 28 comprising three irregularly shapedconductors.
 30. A sensor according to claim 29 wherein a firstirregularly shaped conductor comprises a length and width of 3 cm, asecond irregularly ring shaped conductor comprises an inner length andwidth of 9 cm and an outer length and width of 15 cm, and a thirdirregularly ring shaped conductor comprises an inner length and width of21 cm and an outer length and width of 27 cm.
 31. A medical imagingsystem comprising a radiation source further comprising at least onecapacitance based proximity sensor; a capacitive sensing circuit; and acontrol system configured to control positioning of said x-ray sourceand proximity sensor.
 32. A system in accordance with claim 31 whereinsaid control system configured to orient said radiation source in atleast one of a horizontal and a vertical direction.
 33. A system inaccordance with claim 31 wherein said proximity sensor configured tomeasure capacitance of an object.
 34. A system in accordance with claim31 wherein said proximity sensor configured to measure capacitance of anobject, when said object is in direct contact with said sensor.
 35. Asystem in accordance with claim 31 wherein said proximity sensorconfigured to measure capacitance of an object, when said object is inproximity of said sensor.
 36. A system in accordance with claim 31wherein an object is a human body said proximity sensor configured tomeasure changes in capacitance as said sensor follows the human bodycontour.
 37. A system in accordance with claim 31 wherein said proximitysensor configured to measure changes in capacitance of an object, whensaid object moves.
 38. A system in accordance with claim 37 wherein anobject is a human body said human body such that said sensor detectsmovement of a raised arm, a crossed leg, a finger wiggling, a toewiggling, and torso motion.
 39. A system in accordance with claim 31wherein said proximity sensor configured to detect capacitive changesomni-directionally.
 40. A system in accordance with claim 31 whereinsaid proximity sensor configured to be re-calibrated based on at leastone of a size, a shape, and a effective sensing surface of an object.41. A system in accordance with claim 31 wherein said proximity sensorconfigured to be re-calibrated based on at least one of a temperatureand a relative humidity of an environment in which an object is placed.42. A system in accordance with claim 31 wherein said capacitive sensingcircuit configured to use charge transfer technology.
 43. A system inaccordance with claim 31 wherein said capacitive sensing circuitconfigured to sense changes in capacitance of at least 15 femtoFarads.44. A system in accordance with claim 31 wherein an object is a humanbody said capacitive sensing circuit configured to sense capacitivechanges to said human body, when said human body is covered with atleast one of paper, plastic, and clothing.
 45. An apparatus comprising:a sensing surface of thin film conducting material; a non-conductingbacking material comprising a front side and a back side, and saidsensing surface mounted on said non-conducting backing.
 46. An apparatusin accordance with claim 45 wherein said apparatus configured to be atleast one of a sensor and a detector.
 47. An apparatus in accordancewith claim 45 wherein said sensing surface is electrically coupled to acapacitive sensing circuit.
 48. An apparatus in accordance with claim 47wherein said capacitive sensing circuit configured to measure a nominalcapacitance at least up to 2500 pF.
 49. An apparatus in accordance withclaim 45 wherein said backing surface is electrically coupled to acircuit ground.
 50. An apparatus in accordance with claim 45 whereinsaid apparatus is configured to be cylindrically shaped.
 51. Anapparatus in accordance with claim 45 wherein said apparatus isconfigured to be an irregular shape.
 52. An apparatus in accordance withclaim 51 wherein said apparatus is configured to be an irregular shapeincluding a angled front side, a flat back side, an open top side, aconvex first side, a convex second side offset from said first side. 53.An apparatus in accordance with claim 45 wherein said sensing materialis configured to cover an outer surface of said apparatus.
 54. Anapparatus in accordance with claim 45 wherein said apparatus isconfigured to be rectangularly shaped.
 55. An apparatus in accordancewith claim 54 wherein said sensing material is configured to be of asmaller surface area than said backing material.
 56. An apparatus inaccordance with claim 45 wherein said sensing surface configured as asingle sensing zone.
 57. An apparatus in accordance with claim 56wherein said sensing zone configured to be electrically coupled to acapacitive sensing circuit.
 58. An apparatus in accordance with claim 45wherein said sensing surface configured to have a plurality of sensingzones.
 59. An apparatus in accordance with claim 58 wherein said sensingzones configured to be electrically coupled to a capacitive sensingcircuit.
 60. An apparatus in accordance with claim 58 wherein saidsensing zones configured to be spaced equidistant from one another. 61.An apparatus in accordance with claim 58 wherein said sensing zonesconfigured to partially cover an outer surface of said apparatus.